<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        /*组选择器 相同的样式 统一设置 用逗号隔开*/
        .div1 ,.div2 ,.div3 {
            width: 100px;
            height: 100px;
            font-size: 20px;
        }

        .div1 {

            background-color: gold;
        }

        .div2 {

            background-color: red;
        }

        .div3 {

            background-color: blue;
        }
    </style>
</head>

<body>


    <div class="div1">1</div>
    <div class="div2">2</div>
    <div class="div3">3</div>


</body>

</html>